/*
 * ptr_ops.c - 指针操作
 */

#include <stdio.h>
int main(void)
{
    int urn[5] = {100, 200, 300, 400, 500};
    int * ptr1, *ptr2, *ptr3;
    ptr1 = urn;
    ptr2 = &urn[2];
    printf("pointer value dereferenceed pointer, pointer address:\n");
    printf("ptr1 = %p, *ptr1 = %d, &ptr1 = %p\n", ptr1, *ptr1, &ptr1);

    ptr3 = ptr1 + 4;
    printf("\nadding an int to a pointer:\n");
    printf("ptr1 + 4 = %p, *(ptr1 + 4) = %d\n", ptr1 + 4, *(ptr1 + 4));

    ptr1++;
    printf("\nvalues after ptr1++\n");
    printf("ptr1 = %p, *ptr1 = %d, &ptr1 = %p\n", ptr1, *ptr1, &ptr1);
    ptr2--;
    printf("\nvalues after ptr2--\n");
    printf("ptr1 = %p, *ptr1 = %d, &ptr1 = %p\n", ptr2, *ptr2, &ptr2);

    --ptr1;
    --ptr2;

    printf("\nPointers reset to original values:\n");
    printf("ptr1 = %p, ptr2 = %p\n", ptr1, ptr2);

    printf("\nsubtracting an int from a pointer\n");
    printf("ptr3 = %p, ptr3 - 2 = %p\n", ptr3, ptr3-2);
    return 0;
}
